The present invention relates to an actuating system for a mode-switching rocker arm device of an internal combustion engine.
Many modern internal combustion engines provide for the selective deactivation of one or more engine valves under predetermined engine operating conditions, such as, for example, during periods wherein demand for engine power is relatively low, to improve fuel economy. Two-step valve actuation, wherein the valves are actuated according to a selected one of a high-lift and a low-lift profile, is similarly used in many modern internal combustion engines. Various devices, generally referred to hereinafter as mode-switching rocker arm devices, are used to achieve valve deactivation and/or two-step valve actuation. Those devices typically require one or more associated actuating devices that enable switching between modes of operation.
In order to accommodate the actuating devices, a specially designed engine cylinder head is likely to be required. Further, such actuating devices are typically operated by fluid/hydraulic pressure. Thus, the actuating devices are relatively slow in operation, and fluid passageways and connections must be provided. The slow operation of the switching/actuating devices can also render the timing and/or sequence of the mode switching event unpredictable. If, when deactivating cylinders, the mode-switching event occurs in the wrong sequence rough engine operation can result. If the mode switching event occurs during the time period when the valve lift event is commencing or about to commence, the mode-switching device may suffer permanent damage or emit undesirable noise (i.e., pin ejection).
Therefore, what is needed in the art is an actuating system that does not require redesign of engine cylinder heads.
Furthermore, what is needed in the art is an actuating system that is operated by the engine camshaft rather than by fluid pressure and thus responds relatively quickly.
Still further, what is needed in the art is an actuating system that does not require associated fluid passageways and/or connections.
Moreover, what is needed in the art is an actuation system that increases the predictability of the mode-switching event and reduces the potential of damage to the mode-switching device.
The present invention provides an actuating system for a mode-switching rocker arm device of an internal combustion engine.
The invention comprises, in one form thereof, an elongate actuator shaft having a central axis that is parallel with and spaced apart from a central axis of an engine camshaft. An actuator lever extends in a generally radial direction from the actuator shaft to engage a locking pin of the rocker arm device. A cam follower engages and is pivotally oscillated relative to the central axis of the actuator shaft by an actuator cam lobe of the engine camshaft. A clutch/brake assembly is associated with the actuator shaft and the cam follower. The clutch/brake assembly is operable to selectively transfer pivotal oscillation of the cam follower to pivotal movement of the actuator shaft and actuator lever to thereby translate the locking pin and cause the rocker arm device to switch modes.
An advantage of the present invention is the need to redesign engine cylinder heads is substantially reduced and/or eliminated.
A further advantage of the present invention is the actuating system is operated by and in timed relation to the engine camshaft, and therefore responds relatively quickly.
A still further advantage of the present invention is the need for associated fluid passageways and/or connections is substantially reduced and/or eliminated.
An even further advantage of the present invention is that it increases the predictability of the actuation event and the mode-switching event.
Yet another advantage of the present invention is that it reduces the potential for damage (i.e., pin ejection) to the mode-switching device.